While a supercavitating propeller is put to practical use, a supercavitating machinery like pump or turbine is not so many. One of the causes is that an interaction in supercavitation between the flow around the rotor or stator and the casing or hub is not clarified. It seems that the interaction is unsteady and the flow behavior is very complex, but in this paper, unsteady inviscid incompressible and small disturbance flow are assumed. An internal flow of axial flow machine is modeled into a flow between paralled plane walls and a velocity distribution is assumed to be the Karman-Prandtl 1/n power law of turbulent flow. Under these assumptions, three-dimensional characteristics of supercavitating hydrofoil between parallel plane walls are analyzed.